Enterobacterales is an order of Gram-negative, non-spore forming, facultatively anaerobic, rod-shaped bacteria with the class Gammaproteobacteria. The type genus of this order is Enterobacter. The order contained a large, diverse group of species, occupying distinct ecological niches and possessing a variety of biochemical characteristics. Many genera within the order have significant impacts on human activity, such as the pathogenic species Escherichia coli, Salmonella enterica, and Yersinia pestis, as well as agriculture-harming phytopathogens such as members of the genera Dickeya, Pectobacterium, Brenneria, Erwinia and Pantoea. The large number of species as well as the range of different biochemical characteristics made describing the order and its subgroups extremely difficult. The assignment and classification of this order was largely based on 16S rRNA genome sequences, which is known to have low discriminatory power and yield different results depending on the algorithm and organism strain used. In addition, these analyses have shown that 'Enterobacteriales' exhibited polyphyletic branching, with distinct subgroups.
In 2016, "Enterobacteriales" was proposed to be reclassified as Enterobacterales, and the type genus changed to Enterobacter in accordance with the International Code of Nomenclature of Prokaryotes.
Molecular signatures
Analyses of genome sequences from Enterobacterales species identified five conserved signature indels (CSIs) for this order in the proteins peptide ABC transporter permease, elongation factor P-like protein YeiP, L-arabinose isomerase, pyrophosphatase, and a hypothetical protein, which in most cases are exclusively shared by either all or most members of this order.